Depends on what shape it's in. When I paid $500 for my 9ft 350 mower I thought I'd done well. Until the next year when I had to rebuild the 'wobble box'. That repair alone was over $500 in parts. Had to replace all the knife sections, wear plates and hold downs this year. Another $200.
If you can, listen to it run so you can pay close attention to the wobble box. Listen for any hard knocking or grinding. Volkswagen Jetta Vr4 Repair Manual download more.
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Those things would indicate bearings failing. Check the knife sections, wear plates and hold downs for wear as well. download free 2017 Mitsubishi Gallant Owners Manual. Hope this helps. Your tractor is plenty big for the JD350.